Wize University Psychology Textbook > Intelligence
Genetic & Environmental Influences
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Genetic & Environmental Influences
To study genetic and environmental influences on intelligence and other traits, we use twin and adoption studies
- Siblings share 50% of their DNA
- Fraternal (dizygotic) twins develop from two different eggs fertilized by two different sperm cells, and also share 50% of their DNA
- Identical (monozygotic) twins develop from one egg fertilized by one sperm cell and share 100% of their DNA
Twin studies compare identical twins with fraternal twins and non-twin siblings to understand the influence of genetics
Adoption studies compare twins and siblings raised together with twins and siblings raised apart to understand the influence of environment
Heritability coefficient - a statistic that describes the proportion of the differences between people on a given trait that can be attributed to differences in their genes
- The heritability of intelligence is approximately .5 to .7, meaning 50-70% of the difference between individuals' intelligence is explained by differences in genetics. The remaining 30-50% is explained by differences in environments
Even in twins, the environment is not 100% identical
- Shared environment - nutrition, household income, etc.
- Non-shared environment - friends, teachers, etc.
Environmental influences on intelligence - poverty, schooling
Researchers are conducting a study on the heritability of intelligence. In order to isolate the influence of genetics, they need to compare which groups?
Practice: Genetic & Environmental Influences II
Researchers discover that the heritability of intelligence is .5. Which of these statements is true?